1. Field of the Invention
The present invention relates to a cover for an air bag disposed on the hub of a steering wheel used in automobiles.
2. Prior Art
In order to reduce personal injuries resulting from most types of automobile accidents, seat belts were installed in passenger vehicles for individuals driving and riding in the vehicle. Although the use of individual seat or safety belts did help reduce personal injuries in most types of vehicle accidents, the driver of the vehicle and the passenger in the front seat of the vehicle, were often thrust forward and injured, particularly in the case of a head-on-collision, when the vehicle comes to a sudden stop. Injury is commonly suffered, because the seat belt, even though properly used, often failed to accord the necessary body restraint to guard against striking or impacting against the steering wheel, the dash board or instrument panel, due to the close proximity of the driver to the steering wheel and the close proximity of the passenger to the instrument panel, respectively.
To provide additional occupant protection, inflatable air bags were installed in such passenger vehicles, to protect the driver and passenger in the front seat. An air bag would be disposed in the hub of the steering wheel to protect the driver and another air bag would be disposed in the instrument panel, in front of the front seat passenger, to protect this passenger. When an accident occurs during driving, a release mechanism is activated by the impact of the vehicle and the folded air bag in the steering wheel and the folded air bag in the instrument panel are inflated rapidly. The persons in the front seat of the vehicle, who are thrown forward by the sudden deceleration of the vehicle, are caught by these inflated air bags, before they impact against any hard objects or sharp edges, and especially before they hit the windshield of the vehicle. The inflation of the folded air bag can be effected in a conventional manner by a gas container or generator. Air bags which are automatically inflated during accidents have the advantage, compared to safety belts alone, in that the latter are only activated by specific actions taken on the part of the occupants in the vehicle, i.e. properly positioning and locking the seat belts. In contrast, air bags are kept ready to immediately function independent of such actions, and they do not inhibit freedom of movement of the occupants in the vehicle.
In the past, when a driver side air bag was inflated, a weakened line on the lid portion of the cover would rupture and the air bag would be deployed. However, sometimes when the air bag deploys in this type of design, the cover breaks into small pieces, scattering and flying into the face of the driver opposite it and/or in the face of the occupants of the vehicle. Another associated problem existing when the air bag deploys, is that forces of considerable magnitude operate on the mounting side wall portions of the air bag cover or those portions of the air bag cover which are affixed to the fixed part of the vehicle.
A proposed solution to this breakage problem was to design a cover having a two layer lid portion comprising, a soft outer surface layer and a rigid inner core layer to which the soft outer surface layer is bonded to; this design obviates the aforementioned problems, in that, as the air bag deploys, the rigid inner core layer is prevented from breaking into small pieces by the outer adhering soft layer. However, such a design has certain problems associated therewith. Among them, is that adequate bonding or adhesion between the two layers is difficult to achieve, because of the extensive contact area between these two layers.
A solution to the breakage problem was to design a unitary cover which substantially eliminated the possibility of the lid portion of the cover, from breaking into small pieces, and scattering within the occupant compartment portion of the vehicle, when the air bag deploys. Such a unitary cover comprises a lid portion having a weakened line which opens when the air bag is deployed. The mounting side wall portions have upper and lower ends, the upper ends of which are connected to the lid portion and the lower ends are adapted for connection to a hub of a steering wheel. The cover is an integral structure. The lid portion comprises a flexible and soft layer, whereas the mounting side wall portions comprise a rigid layer; the two layers are united at their points of contact or where their materials come together. Such a cover is disclosed in U.S. patent application Ser. No. 07/955,419, filed Sep. 22, 1992 entitled "Air Bag Cover And Method Of Manufacturing The Cover".
Accordingly, it is an object of this invention, to provide an improved driver side air bag cover, used in an automobile.
Another object of the present invention is to provide an improved driver side air bag cover, which deploys, in a safe and reliable manner, when the air bag inflates.
A still further object of the present invention, is to provide a driver side air bag cover, which eliminates the possibility of the lid portion of the cover, from breaking into small pieces, and scattering within the occupant compartment portion of the automobile, when the air bag deploys.
A further object of the present invention, is to provide a driver side air bag cover, having lateral mounting side wall portions, which detach from the base plate they are attached to, and an upper mounting side wall portion, which remains attached to the base plate, when the air bag deploys.